The present invention concerns an air knife for directing a stream of air against a surface. One application for the invention is for applying air against moving pieces of glass for use in fabricating windows.
Existing air knives direct air at a high velocity from an elongated housing to create a curtain of air that can be directed against a surface. In the art of window fabricating, glass sheets are shipped from a supplier, unloaded, cut, and washed. The washing process removes a packing material, such as Lucor, that makes the glass sheets easier to separate from each other. The washing process also cleans the glass so that adhesives properly adhere to the glass sheets after they exit the washer. The sheets are dried by an air knife and moved to another fabrication station where, for example, they are assembled into a door, a window, or an insulating glass unit.
Existing or prior art air knives greatly increase noise levels in the region in which they operate. Such noise is due to the fact that the air escaping from a chamber or housing creates a first sound and additionally a blower that delivers air to the prior art air knife adds to the noise. The combined noise from the air knife and the blower can be loud enough to require operators in the vicinity of the glass washer to wear ear plugs to lower the noise level the worker experiences. Additionally, use of high power blowers adds to the expense of operating these prior art air knives. Existing air knives are constructed using extruded tubes that are assembled into a completed air knife. One goal of the invention is to provide an efficient and less costly air knife than existing commercially available air knives.
An air knife constructed in accordance with the present invention directs a stream of air across a region and most typically is used to direct the stream of air against a surface. In an exemplary embodiment of the invention the air knife includes an elongated housing having an inlet for receiving air into the housing. The housing includes an elongated gap that allows air entering the housing through the inlet to exit the housing and form a stream of air. The elongated housing is made from one or more pieces of sheet metal bent to define a hollow region into which air is forced. The sheet metal defines a gap along a length of the housing from which the air exits.
Another aspect of the invention is a method of fabricating an air knife including providing a sheet of metal having a length substantially equal to a length of the air knife. A housing is formed by bending the sheet metal and bringing opposing edges of the sheet metal into spaced relation with each other to form a gap through which air can escape from an interior of the housing during operation of the air knife. The interior region of the housing is coupled to a source of pressurized air so that air exiting the housing forms a stream of air that passes through a controlled region in relation to the housing.
The exemplary embodiment of the invention is for use in drying a sheet of material that moves in relation to the air knife. Other uses of the knife will be readily apparent to those having applications that require a directed stream of air that passes through a region. The disclosed air knife operates at a noise level lower noise level than prior systems and which is low enough to enable an operator to stand in the vicinity of the air knife without wearing special ear plugs and also without the use of expensive muffling equipment for the blower.
An exemplary air knife is made from two elongated bent pieces of sheet metal that are bent to form two members that mate to form a housing. A third member that is also made from an elongated sheet of metal form an elongated nozzle that defines the gap which extends along a length of said housing. In this construction, the first and second members form a first chamber into which air is delivered by a blower and the third member combines with one of said first and second members to define a second chamber which receives air from the first chamber and dispenses air through the gap to form a stream of air.
The resulting structure can be built more cheaply than existing air knives. It is believed that the cost per unit length of air knives constructed in accordance with an exemplary embodiment of the invention can be made at significantly reduced costs.